As a process for production of a crayon, a method has been conventionally known which involves adding a resin component to an appropriate organic solvent, stirring the mixture to prepare a solution, adding thereto a colorant and dissolving or dispersing the colorant therein to form a solution or a dispersion, adding thereto a benzylidene sorbitol gelling agent, such as dibenzylidene sorbitol, and dissolving the gelling agent therein under heating, pouring the resultant into a molding container having a cylindrical shape, for example, and then cooling and solidifying the same (see Patent Literature 1).
As another example of a process for production of a crayon using a benzylidene sorbitol gelling agent together with the use of carbon black as a colorant, a method has been known which involves dissolving a first resin component in an organic solvent, adding carbon black to the obtained resin solution and dispersing the carbon black therein, adding a benzylidene sorbitol gelling agent to the solution under heating and dissolving the gelling agent therein, adding thereto a second resin component at the same temperature and dissolving the second resin component therein, pouring the solution thus obtained into a molding container, and cooling and solidifying the resultant (see Patent Literature 2).
In producing a crayon using the benzylidene sorbitol compound as a gelling agent together with the use of carbon black as a black pigment in particular in a manner as described above, poor gelation frequently occurs in a final gelling process, resulting in that a crayon cannot be stably produced. More specifically, in the production of a crayon, a resin component and carbon black are dissolved and dispersed, respectively, in an organic solvent, a benzylidene sorbitol gelling agent is dissolved in the resultant under heating to prepare a raw material solution, the raw material solution is poured into a molding container, depending on the case, while continuously heating the raw material solution so that the gelling agent remains dissolved in the raw material solution, and when the solution is cooled and solidified, it frequently happens that the gelling agent does not function, resulting in poor gelation.
When a heating time for dissolving the gelling agent is short, it is difficult to uniformly dissolve the gelling agent in an organic solvent, and thus a homogeneous crayon cannot be obtained. On the other hand, when a heating time is long, poor gelation occurs when the obtained raw material solution is poured into a molding container and, cooled and solidified. The crayon thus obtained does not have a required gel hardness, and thus the crayon is easy to collapse in writing, resulting in difficulty of writing. Depending on the case, the solution does not gel, and thus a crayon cannot be obtained.    Patent Literature 1: Japanese Patent Publication No. 54-23619    Patent Literature 2: Japanese Patent Publication No. 55-41716